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Posts Tagged ‘astrophysics

“Oh, there you are Peter”*…

 

The missing links between galaxies have finally been found. This is the first detection of the roughly half of the normal matter in our universe – protons, neutrons and electrons – unaccounted for by previous observations of stars, galaxies and other bright objects in space.

You have probably heard about the hunt for dark matter, a mysterious substance thought to permeate the universe, the effects of which we can see through its gravitational pull. But our models of the universe also say there should be about twice as much ordinary matter out there, compared with what we have observed so far.

Two separate teams found the missing matter – made of particles called baryons rather than dark matter – linking galaxies together through filaments of hot, diffuse gas

Get galactic at: “Half the universe’s missing matter has just been finally found.”

* meme

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As we heed E.M. Forster, we might recall that it was on this date in 1843 that Sir William Rowan Hamilton conceived the theory of quaternions.  A physicist, astronomer, and mathematician who made important contributions to classical mechanics, optics, and algebra, he had been working since the late 1830s on the basic principles of algebra, resulting in a theory of conjugate functions, or algebraic couples, in which complex numbers are expressed as ordered pairs of real numbers.  But he hadn’t succeeded in developing a theory of triplets that could be applied to three-dimensional geometric problems.  Walking with his wife along the Royal Canal in Dublin, Hamilton realized that the theory should involve quadruplets, not triplets– at which point he stopped to carve carve the underlying equations in a nearby bridge lest he forget them.

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Written by LW

October 16, 2017 at 1:01 am

“It’s the end of the world as we know it”*…

 

“The probability of global catastrophe is very high,” the Bulletin of the Atomic Scientists warned in setting the Doomsday Clock 2.5 minutes before midnight earlier this year. On nuclear weapons and climate change, “humanity’s most pressing existential threats,” the Bulletin’s scientists found that “inaction and brinkmanship have continued, endangering every person, everywhere on Earth.”

Every day, it seems, brings with it fresh new horrors. Mass murderCatastrophic climate changeNuclear annihilation.

It’s all enough to make a reasonable person ask: How much longer can things go on this way?

A Princeton University astrophysicist named J. Richard Gott has a surprisingly precise answer to that question…

Gott applies straight-forward logic and the laws of probability to setting our exit date.  “Calculations” haven’t worked out so well for Mayan seers or the likes of Harold Camping; but as you’ll read, Gott has tested his method, and done remarkably well… so: “We have a pretty good idea of when humans will go extinct.”

* REM

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As we plan our parties, we might recall that it was on this date in (what we now call) 46 BCE, that the final year of the pre-Julian Roman calendar, began.  The Romans had added a leap month every few years to keep their lunar calendar in sync with the solar year, but had missed a few with the chaos of the civil wars of the late Republic. Julius Caesar added two extra leap months to recalibrate the calendar in preparation for his calendar reform, which went into effect in (what we now now as) 45 BC.  The year, which had 445 days, was thus known as annus confusionis (“year of confusion”).

Fragmentary fresco of a pre-Julian Roman calendar

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Written by LW

October 13, 2017 at 1:01 am

“Magnetism, you recall from physics class, is a powerful force that causes certain items to be attracted to refrigerators”*…

 

Concentric incision on a jar handle from Ramat Rahel, in modern-day Israel

Of all the environmental amenities that this hospitable planet provides, the magnetic field is perhaps the strangest and least appreciated. It has existed for more than three and a half billion years but fluctuates daily. It emanates from Earth’s deep interior but extends far out into space. It is intangible and mostly invisible—except when it lights up in ostentatious greens and reds during the auroras—but essential to life. The magnetic field is our protective bubble; it deflects not only the rapacious solar wind, which could otherwise strip away Earth’s atmosphere over time, but also cosmic rays, which dart in from deep space with enough energy to damage living cells. Although sailors have navigated by the magnetic field for a millennium and scientists have monitored it since the eighteen-thirties, it remains a mysterious beast. Albert Einstein himself said that understanding its origin and persistence was one of the great unsolved problems in physics…

Direct measurements of the magnetic field now span almost two hundred years, and iron-rich volcanic rocks on the ocean floor provide a lower-fidelity chronicle of its erratic behavior—including wholesale reversals in polarity—back about a hundred and fifty million years. But reconstructing the field’s behavior between these two extremes has been difficult. The trick is to find an iron-bearing object that locked in a record of the magnetic field at a well-constrained time in the past, in the way that wine of a given vintage preserves an indirect record of that year’s weather conditions…

Last Monday, in a study published in Proceedings of the National Academy of Sciences, a team of Israeli and American archeologists and geophysicists reports the most detailed reconstruction yet of the magnetic field in pre-instrumental times, using a set of ceramic jars from Iron Age Judea…

In the geophysical community, the tales told by the Judean jars may cause unrest. Both the height and the sharpness of the spike they recount push up against the limits of what some geophysicists think Earth’s outer core is capable of doing. If the eighth-century-B.C. geomagnetic jeté is real, models for the generation of the magnetic field need significant revision. Given the importance of a stable magnetic field to our electricity-dependent, communications-obsessed culture, these questions are of more than academic interest…

More on these befuddling fields at “Earth’s mysterious magnetic field, stored in a jar.”

* Dave Barry

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As we look for True North, we might send undulating birthday greetings to George Fitzgerald Smoot III; he was born on this date in 1945.  An astrophysicist and cosmologist, Smoot discovered the signature of gravitational waves– ripples in space-time were first predicted by Albert Einstein– in his study of the cosmic microwave (“background”) radiation that originated with the Big Bang.  He won the Nobel Prize in Physics in 2006; three years later he became the second person to run the board on the quiz show Are You Smarter than a 5th Grader?, and took home the $1 million grand prize.

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Getting small…

More pixie-like pix at Slinkachu‘s “Little People Project” (“abandoning little people on the streets since 2006”)…

[TotH to Laughing Squid and Sex + Design]

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As we keep everything in perspective, we might send a bright metal birthday riff to Brian Harold May, CBE; he was born on this date in 1947.  Rightly known for his work as guitarist, songwriter and occasional singer of the band Queen (he is ranked 26th on Rolling Stone‘s list of Greatest Guitarists of All Time, and 7th on Planet Rock‘s), he has also distinguished himself as an astrophysicist.  During a hiatus from the band, May completed his PhD at Imperial College (which he’d left in abeyance in the early 70s to pursue Queen); his dissertation was A Survey of Radial Velocities in the Zodiacal Dust Cloud.  Asteroid 52665 Brianmay was named in his honor in June, 2008 at the suggestion of British Astronomical Association President Sir Patrick Moore.

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Written by LW

July 19, 2012 at 1:01 am

Time is an illusion. Lunchtime doubly so*…

 

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From Sean Carroll, theoretical physicist at Cal Tech and author of From Eternity to Here, a report from Setting Time Right, a conference that he kicked off in Norway late last month…

“Time” is the most used noun in the English language, yet it remains a mystery. We’ve just completed an amazingly intense and rewarding multidisciplinary conference on the nature of time, and my brain is swimming with ideas and new questions. Rather than trying a summary (the talks will be online soon), here’s my stab at a top ten list partly inspired by our discussions: the things everyone should know about time. [Update: all of these are things I think are true, after quite a bit of deliberation. Not everyone agrees, although of course they should.]

Sean’s list– like his books, clear and provocative– is at “Ten Things Everyone Should Know About Time.”

* – Douglas Adams

 

As we wind our watches, we might recall that it was on this date in 2008 that two of Carroll’s ten points– #4 (“You live in the past”) and #9 (“Aging can be reversed”)– were illustrated, as MTV threw the full weight of its VMA Awards behind Britney Spears’ comeback.  Spears performed on the telecast and won three awards, including video of the year for “Piece of Me.”  The following year she completed her highest-grossing global concert tour.

Oops!… I Did It Again (source)

 

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